Yes, having unilateral control of your funds is self custody.
Now with Spark there are some caveats to this but it has nothing to do with the wider privacy conversation.
Discussion
Sure. If Spark releases software that anyone can run, that does not "phone home" to LightSpark.com, and allows me to exit out of their ecosystem onto onchain Bitcoin, that does seem at least fairly close to "self custody".
BTW -- I think Ark should think about this, and when you are ready to go consumer-facing, be proactive about showing that anyone can run and endpoint, and it's totally possible for someone to interact with Ark without touching Arkade's domains. Even if you have a couple small-time operators stand up the service, make it available on their domains, that would be huge.
Self custody has no concept of privacy. By your standards most people self custodying are not actually self custodying. This does not align with reality.
Unfortunately you don’t seem to understand how these systems work. We have docs if you’re interested.
Got it! Still hoping that Arkade finds a way to be decentralized....